What is the value of an 1867 us half dime?

Look on the back of the coin to see if there's a small mint mark letter below the Word DIME. It may be blank or there may be an S.

Numismedia lists the following approximate retail values as of 08/2014:

No mint mark (Philadelphia):

Very worn condition - $535

Moderately worn - $620

Slightly worn - $750

Almost no wear - $1,028

Uncirculated - $1,180 to $6,830 depending on quality

"S" mint mark (San Francisco)

Very worn - $23

Moderately worn - $37

Slightly worn - $78

Almost no wear - $319

Uncirculated - $600 to $6,410

Beware of "S" mint coins that have had their mint mark removed.

This now seemingly-strange denomination was the only 5¢ coin minted by the US until nickels were introduced in 1866. It fit into the 1/2 - 1 pattern of early coinage, e.g. half-cent, cent; half-dime, dime; half-dollar, dollar; etc. After enough nickels had been made, half dimes were discontinued in 1873.

DISCLAIMER: The retail values quoted are the best available as of the date shown, but may vary significantly due to changes in the precious metals market. Also the wholesale (buying) price of a coin will be less than the selling (retail) price. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.